The present invention relates to a flying head of a magneto-optical recording apparatus, and particularly relates to an improved flying head having a superior response to a high frequency and being capable of forming a strong and uniform magnetic field toward the surface of a magneto-optical recording medium.
First the principle of recording in a magneto-optical recording apparatus will be described with reference to FIG. 8. In FIG. 8, the reference numeral 81 represents a recording film constituted by a magnetic material, 82 represents an objective lens, 83 represents a coil, and 84 represents a laser light. The recording film 81 is magnetized in a predetermined direction as shown in FIG. 8(A). This state shows an erasing state. As shown in FIG. 8(B), a current is supplied to the coil 83 to generate a magnetic field in the direction of arrow opposite to the magnetized direction of the recording film 81, and the laser light 84 is focused onto a recording area of the recording film 81 by the objective lens 82 at the same time, thereby irradiating a laser spot to the recording film 81 which is in an erasing state. By the irradiation of a laser spot, it is possible to invert the magnetized direction of a recording portion to thereby perform recording. On the other hand, in order to perform erasure, as shown in FIG. 8(C), a current having a direction opposite to that at the time of recording is supplied to the coil 83 to invert the direction of a magnetic field, and a laser spot is irradiated to a recording portion of the recording film 81 in this state, so that the magnetized direction of the irradiated portion can be returned to the state before recording so as to be in an erasing state.
FIG. 9 is a diagram for explaining the principle of readout. If laser light is irradiated to a recording film in which magnetization recording is performed as explained in FIG. 8, the Kerr rotation angle of its reflected or transmitted wave is changed by the direction of magnetization as shown in the arrow 84a or 84b. By detecting such a change of the Kerr rotation angle, it is possible to readout recorded information.
By the way, a flying head disclosed in Japanese Unexamined Patent Publication No. Sho-60-261052 has been known as an optical head for performing information recording, information readout and information erasing in such a magneto-optical recording apparatus.
FIGS. 10 to 12 show such a flying head, FIG. 10 being a schematic view of the whole, FIG. 11 being an expanded view of a head body portion, FIG. 12 being a sectional view taken on line A--A of the head body portion in FIG. 11. In FIGS. 10 to 12, the reference numeral 100 represents a magneto-optical recording medium, 101 represents a flying head body portion, 102 represents an air slider, 103 represents a reflective prism, 104 represents a light path aperture portion, 105 represents an objective lens, 106 represents a setting groove, 107 represents a coil, 108 represents a coupling arm, 109 represents a driving portion, 110 represents a light source, and 111 represents a light beam.
The flying head body portion 101 is driven by the driving portion 109 through the coupling arm 108 so as to be moved in the radial direction of the magneto-optical recording medium 100 to thereby be positioned. The air slider 102 is formed of a soft magnetic material so as to be floated by an air stream caused by the revolution of the magneto-optical recording medium 100. In the flying head body portion 101, the light path aperture portion 104 is formed in a portion of the air slider 102, and the lens 105 is provided in the light path aperture portion 104, as clearly shown in FIG. 12. In addition, the reflective prism 103 is fixed on the light path aperture portion 104. The light beam 111 from the light source 110 is incident to the reflective prism 103, reflected downward, and focused through the lens 105 onto the magnetic film surface of the magneto-optical recording medium 100. The coil 107 as a magnetic field generating means is wound in the setting groove 106 provided along the aperture edge of the aperture portion 104 on the side of the magneto-optical recording medium 100, so that a magnetic field for writing or erasing can be generated in the magneto-optical recording medium 100 by a current flowing through the coil 107.
In this flying head body portion 101, the coil 107 is mounted on the side of a head, so that there is an advantage to simplify a driving means thereof in comparison with an apparatus, and only the minimum members such as the reflective prism 103, the lens 105, the coil 107 and so on are mounted on the air slider 102, so that it is possible to lighten the head and shorten access time. In addition, the air slider 102 is made to float by an air stream caused by the revolution of the magneto-optical recording medium 100. It is therefore possible to maintain a constant distance between the magneto-optical recording medium 100 and the air slider 102, so that there is an advantage to simplify a focusing mechanism for the lens 105.
In such a flying head, however, the magnetic resonance frequency of its coil system is near 20 MHz, so that there has been a problem that it is difficult to switch the direction of a magnetic field at a high speed not lower than 20 MHz.
On the other hand, an apparatus using a thin film magnetic head with a high resonance frequency as a magnetic field generating means has been reported by Stephane RENARD, et al., "Magneto Optical Reading and Writing Integrated Heads A Way to a Multigigabyte Multi-rigid-disk Drive", OPTICAL DATA STORAGE, (1991), p. 238-247.
FIG. 13 shows a head portion of a magneto-optical recording apparatus using a thin film magnetic head. In FIG. 13, the reference numeral 130 represents a magneto-optical recording medium, 131 represents a flying head body portion, 132 represents an air slider, 133 represents a thin film magnetic head, 134 represents an optical integrated circuit, 135 represents optical fibers, and 136 represents a coupling arm. The flying head body portion 131 is made to float on the magneto-optical recording medium 130 by the air slider 132, and is positioned in a writing or reading track by the coupling arm 136 in the same manner as that in the magneto-optical recording apparatus which has been described with reference to FIGS. 10 to 12. However, light from a light source is led to the flying head body portion 131 through the optical fibers 135. Three fibers are illustrated as the optical fibers 135. One is for input light for writing or reading, and the other two are for outputting light which has been read. These optical fibers 135 are connected to the optical integrated circuit 134. Required branching and connecting circuits are formed in the optical integrated circuit 134, and coupled with a light waveguide path shown in FIG. 14. The thin film magnetic head 133 as a magnetic field generating means is provided on the side edge of the air slider 132 near the optical integrated circuit 134.
FIG. 14 is a sectional view of the flying head body portion 131. Laser light incident from the optical integrated circuit 134 is led to a light waveguide path 142 through an integrated mirror portion 141, and irradiated as laser beam light focused onto a not-shown magneto-optical recording medium disposed below. The reflected light from the magneto-optical recording medium is coupled with the optical integrated circuit 134 through the light waveguide path 142 and the integrated mirror portion 141. The curve L shows the space distribution of the light power of the light irradiated through the light waveguide path 142, and according to the curve L the maximum of the light power is at the center of the light waveguide path 142. The reference numeral 143 represents a thin film magnetic head, which is provided near the light waveguide path 142. The thin film magnetic head 143 is constituted by a pole 144 of a soft magnetic material, a non-magnetic layer 145, a coil 146, a protective layer 147 for the coil 146, and a yoke 148 of a soft magnetic material. The coil 146 is formed into a disc-like wound shape, and its sectional view taken in its diameter direction passing its center is illustrated. If a current is supplied to the coil 146, a magnetic path is formed between the pole 144 and the yoke 148, so that a vertical magnetic field is applied to a not-shown magneto-optical recording medium. The curve M illustrated in the lower side shows the distribution of the intensity of the magnetic field.
In this flying head body portion 131 described in FIGS. 13 and 14, only the minimum members are mounted on the air slider 132, so that it is possible to lighten the flying head body portion 131 and to shorten access time. In addition, the air slider 132 is made to float by an air stream caused by the revolution of the magneto-optical recording medium 130, so that it is possible to maintain a constant distance between the magneto-optical recording medium 130 and the air slider 132. It is therefore possible to simplify a focusing mechanism for the integrated mirror portion 141. In addition, the thin film magnetic head 143 itself is so small as to take a small self-inductance value and a high resonance frequency, so that there is an advantage to make it possible to switch a magnetic field at a high frequency near 100 MHz.
A flying magneto-optical head similar to this has been disclosed in Japanese Unexamined Patent Publication No. Sho-58-118026. This magneto-optical head has a thin film magnetic head 152 on the side surface of a flying body 151 as shown in FIG. 15, focusing a light beam 154 onto a recording portion of a magneto-optical recording medium 150 by use of an objective lens 153. The reference numeral 155 represents a gimbal, and 156 represents an arm.
Although the flying head mounted with a thin film magnetic head described with reference to FIGS. 13 and 14 has such an advantage as mentioned above, there has been a problem that the peak position of distribution of intensity of a vertical magnetic field obtained from the thin film magnetic head does not correspond to the peak position of distribution of intensity of a laser beam irradiated onto a magneto-optical recording medium through an integration mirror as has been described with reference to FIG. 14, and a desired magnetic field is obtained far from the peak position, so that it is necessary to supply a higher current, and the ability of the thin film magnetic head cannot be used effectively. In addition, an optical system constituted by a light waveguide path often has a coupling efficiency with an optical fiber about 10%, so that there has also been a problem that the efficiency of using light is low.
A flying head described with reference to FIG. 15 has an optical system constituted by optical parts such as a lens, and the optical parts are provided on the side surface of the flying body, so that there has been a problem that the stability at the time of flying and running is poor.